Lake Pocotopaug Lake and Watershed Restoration Evaluation ...

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elow 7:1 occurred on September 22, 1993 at surface and mid depths and occurred in May,August, and September in 1993 at the bottom.The trophic state of Lake Pocotopaug, determined as Carlson’s (1977) trophic state index (TSI)from July and August SDT, surface TP, and chlorophyll a (chl a) values was typical ofmesotrophic conditions (intermediate nutrient levels) during summer stratification. TSI valueshigher than 60 are indicative of degraded (eutrophic) conditions, while TSI values below 40typically apply to oligotrophic lakes (Carlson 1977). Mitchell (2000) proposes a TSI=70threshold for contact recreation. TSI for all categories were below 60 but above 40.Using July and August data from 1991-2001, the trophic state of Lake Pocotopaug, asdetermined from the State of Connecticut Water Quality Standards, is mesotrophic,(intermediate nutrient levels). Table 11 compares Lake Pocotopaug range of means with StateWater Quality Standards for mesotrophic conditions.Table 11. Lake Pocotopaug July and August Range of Annual Means and Water QualityStandards for Mesotrophic Lakes in Connecticut.Mesotrophic Standard Lake PocotopaugAnnual Mean Range(July and August)TP 10-30 ug/L spring and summer 11-23TN 200-600 ug/L spring and summer 440Chl a 2-15 ug/L mid summer 5.5-7.4SDT 2-6 meters mid summer 0.7-3.5Dissolved iron provides a measure of the potential of a water body to limit phosphorus internalloading. Ferrous iron (Fe ++ ) is often released from anoxic sediments along with dissolvedphosphorus (DP). Ferric iron (Fe +++ ) is the dominant form of iron in the presence of oxygen, andforms from Fe ++ . Iron tends to bind with phosphorus during this conversion and, because of lowsolubility, iron phosphates precipitate to the sediment.Dissolved iron concentrations just above the water-sediment interface provide a measure of thepotential for release of sediment-bound phosphorus and its return to the sediments. Dissolvediron values much higher than 1.0 mg/l are often indicative of substantial redox activity in thesediments, whereby chemical oxidation-reduction reactions can allow certain contaminants tobe released from the sediment back into the water column. However, dissolved iron in excessof ten times the DP level is usually sufficient to precipitate out all DP under oxic conditions, sophosphorus released by this mechanism will not necessarily be available for algal uptake andgrowth.Lake Pocotopaug Restoration Evaluation 38May 2002
Dissolved iron concentrations at the water-sediment interface in Lake Pocotopaug wasmeasured in August 2001. Values were low, below the 0.01 mg/L detection limit at both stationsand all water depths (Table 10). These low values in the summer suggest a low phosphorusbinding capacity in Lake Pocotopaug.Total and dissolved aluminum were analyzed in 2001 prior to the alum treatment. Totalaluminum ranged from 0.036 to 0.794 mg/L. Dissolved aluminum was below the detection limit.Aluminum is not list on the State of Connecticut Water Quality Standard Numerical Criteria, butthese values are consider relatively low. In addition, arsenic, cadmium, chromium, copper,nickel, lead, and zinc were analyzed in May 2001. All values were low (Table 10) and suggestno water column metal contamination in Lake Pocotopaug.6.2 Tributary and Storm Drain Water Quality2001 water quality data for tributaries and storm drains are presented for both dry and wetweather in Table 12. Data collected in March of 2001 by the CT DHS are included in thissummary. Locations of the incoming water stations are given in Figure 6 and Table 9.Generally, stormwater sampling resulted in higher concentrations with the exception of pH,chloride, hardness, conductivity and nitrate. This may indicate that there are constant sources,which are being diluted during precipitation, and/or precipitation itself (acid rain) is loweringthese values.Lake Pocotopaug Restoration Evaluation 39May 2002
Page 2 and 3: LAKE POCOTOPAUGLAKE AND WATERSHEDRE
Page 4 and 5: 11.3 Prevent algal blooms from occu
Page 6 and 7: LAYPERSON’S SYNOPSISLake Pocotopa
Page 8 and 9: The stocking of walleye in Lake Poc
Page 10 and 11: Lake Pocotopaug Restoration Evaluat
Page 12 and 13: Period Covered 1988• Pollution fr
Page 14 and 15: Recommendations included• Algacid
Page 16 and 17: Major EventDecember 1999 - Fish kil
Page 18 and 19: Table 5. Land Use from the CT DEP G
Page 22 and 23: Figure 4. Lake Pocotopaug Bathymetr
Page 24 and 25: Table 6. QA/QC on Water Quality Dat
Page 26 and 27: Soils - USDA at MAGIC UCONN Geograp
Page 28 and 29: Table 8. Water Quality Variables Me
Page 32 and 33: Phytoplankton samples were collecte
Page 34 and 35: where many measurements would have
Page 36 and 37: Figure 7. 2001 Temperature and Diss
Page 38 and 39: Table 10 continued. 2001 Lake Pocot
Page 40 and 41: phytoplankton biomass (Wetzel 1983)
Page 42 and 43: Figure 9. Annual June, July and Aug
Page 46 and 47: Table 12. 2001 Dry and Wet Weather
Page 48 and 49: Table 12 continued. 2001 Dry and We
Page 56 and 57: were identified to genus and enumer
Page 58 and 59: Table 13 continued. 2001 Phytoplank
Page 68 and 69: Figure 10. 2001 Phytoplankton Bioma
Page 70 and 71: The late summer bloom of blue-green
Page 72 and 73: Table 15. 2001 Zooplankton DensityZ
Page 74 and 75: Table 16. 2001 Zooplankton BiomassZ
Page 76 and 77: 7.0 RELATIONSHIPS AND TRENDS7.1 Pre
Page 78 and 79: Figure 13. 1991-2001 Surface Water
Page 80 and 81: Figure 15. 2001 Surface and Mid-dep
Page 82 and 83: Figure 16. 1991-2001 Chlorophyll a
Page 84 and 85: Figure 18. 2001 Chlorophyll a vs. S
Page 86 and 87: Figure 20. 1991-2001 July and Augus
Page 88 and 89: Table 17. Empirical Model Calculati
Page 90 and 91: Table 18. Total Phosphorus Loading
Page 92 and 93: Table 19. Wet Weather Loading Summa
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With the best possible treatment of
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water quality should focus on input
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10.0 MANAGEMENT NEEDS AND OBJECTIVE
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11.2 Reducing Total Phosphorus and
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undeveloped forest land, an opportu
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Figure 22. Buffer Strips for Pollut
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Figure 23. Catch Basin with Sump an
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early spring to capture what appear
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Figure 26. Infiltration Systems.Lak
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Figure 27. Constructed Treatment We
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Chemical TreatmentIn-stream chemica
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TABLE 21. MANAGEMENT OPTIONS FOR CO
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TABLE 21 continued. MANAGEMENT OPTI
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12.0 ADDITIONAL DATA NEEDSManagemen
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13.0 RECOMMENDED MANAGEMENT PROGRAM
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this point, but as a rough guide, a
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14.0 REFERENCESAd Hoc Lake Advisory
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Scheuler T.R., P.A. Kumble, & M.A.
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Appendix B:Supplemental Tables and
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Appendix D:Educational MaterialsLak
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